Interpretive Summary: In recent years, a fungus that causes a disease of wheat known as Fusarium head blight (FHB) has become more common in many of the wheat growing regions of the world. Traditional measures for controlling this disease such as disease-resistant varieties of wheat and fungicides are not very effective. Biological control, which can be defined as the use of naturally occurring microorganisms to control pests, has considerable promise for reducing this disease. A unique biological control strategy that combines seed pretreatment with a biocontrol agent named "Mycol" (Trichoderma asperellum strain GJS 03-35, discovered in Russia) with spraying wheat plants during flowering with a yeast Cryptococcus nodaensis OH 182.9 (NRRL Y-30216, discovered by an Agricultural Research Service scientist) is being developed. In the present study, we tested whether coating seed with the Mycol biological control agent before planting, or spraying wheat heads with one of the two biological control agents would influence the level of Fusarium head blight that developed. We found that the biological control treatments were both effective in reducing the severity of disease and in reducing by 6 to 10 times the amount of a toxin that the pathogen can sometimes produce. The Mycol treatment also increased the weight of seed that was produced and both biological control treatments enhanced the germination of seed obtained from treated heads. Developing technology for reducing FHB based on a combination or single one of these two biological agents has good prospects for reducing this devastating disease of wheat field under field conditions.

Technical Abstract:
In recent years, intense disease pressure by Fusarium head blight of wheat has been reported throughout wheat producing regions of the world that commonly experience rainfall during wheat flowering. Methods for controlling this disease and reducing the associated deleterious effects of mycotoxins produced by the pathogen are not very effective. A unique biocontrol strategy that combines seed pretreatment with a biofungicide “Mycol” (Trichoderma asperellum strain GJS 03-35) with spraying wheat plants during flowering with the yeast Cryptococcus nodaensis OH 182.9 (NRRL Y-30216) is being developed. In the present study, tests with the Mycol preparation and the yeast OH 182.9 (EOD) were performed on the spring wheat "Ivolga" in greenhouse conditions in the Moscow region of Russia. Seed coating with Mycol and application of Mycol” or C. nodaensis at the time of flowering reduced FHB severity while the fungicide Tiram did not. One-thousand kernel weight was increased by seed or head treatment with Mycol but not by the treatment with C. nodaensis alone. Both biological control treatments singly or in combination reduced DON content by 6 to 10 times. Seed from wheat that had been treated with one or both biological control agents exhibited enhanced levels of germination compared to the controls. Experimental results support the contention that this biological control technology has good prospects for reducing FHB under field conditions.